1. Field of the Invention
This invention relates to armored tires having a traction plate equipped ground engaging surface. More specifically this invention is concerned with the implantation of a specially equipped anchor plate in the carcass of a tire to provide a high strength mounting means for the traction plates. The anchor plates are molded between the inner plies of the tire and an elastomer insulated fabric and inextensible filament anchor ply structure.
2. Description of the Prior Art
Pneumatic tired vehicles which work in construction and other harsh environments are oftentimes driven on extremely detrimental road surfaces. Numerous articulated and conventional loaders, scrapers, dump trucks and graders, etc. operate in rock quarries, mines, foundries, refuse yards and other sites where the tires of the vehicle are continually exposed to puncture producing and wear inducing elements.
As the tires for large construction type vehicles are expensive it is economically advantageous to minimize exposure to tire damaging elements. One way that this tire wear problem may be alleviated is through the use of endless track vehicles. Conventional two tracked vehicles are equipped with endless tracks made up of traction or grouser plates and linking members which are normally driven by sprocketed wheels. Two track vehicles have high tractive efficiency, good stability, and good floatation characteristics while also having the advantage of infrequent track failure resulting from damage caused by the working environment. Bulldozers, power shovels, and cranes are often seen with dual endless track ground engaging means.
Conversely, endless track vehicles do have certain disadvantages that make them undesirable in some material handling situations. Two track vehicles have speed limitations due to the track assembly and are not capable of adequately dampening road shocks and vibrations. The amount of heat generated by the track links may be severe enough at high speeds to cause premature failure of the tracks.
In a vehicle having pneumatic tires the tires are capable of relatively high speed while also providing a major portion of the shock dampening function of the vehicle suspension. Thus for construction vehicles, such as loaders and dump trucks, which operate at high speed a pneumatic tire is economically advantageous. In order to realize the benefits of the endless track and the pneumatic tire it is highly desirous to combine the armor protection of a traction plate with the high speed capability of a pneumatic tire.
Many attempts to armor tires using plates held in position on the tire by means of chains, links, cables, etc. have been tried for special applications. Specific examples of tracks linked over tires are shown by U.S. Pat. No. 3,601,212 to Peterson, et al and to U.S. Pat. No. 3,612,624 to Stedman. These adaptations of linked tracks and pneumatic tires provide for a shock dampening advantage as well as tire armoring, however, the linked track limits the speed of the vehicle due to the high frictional heat build-up in the linking components which may cause a high rate of wear.
The troublesome link track systems of early evolutionary developments have been improved upon by several inventions as typified by the invention disclosed in U.S. Pat. No. 3,773,394 to Grawey. In this invention the traction plates are fastened to anchor plates which accommodate a plurality of independent circumferential belts. This belt structure is positioned on the crown of a pneumatic tire and the tire is inflated into the belt and track assembly. The belts have been formed and cured before their assembly with the anchor plates and traction plates. A continuous interior belt surface contacts the pneumatic tire carcass and provides frictional engagement therewith.
Although the state of the art flexible belt system of linking track shoes together is operational this two piece tire and belt system does present some drawbacks. For instance, as the circumferential belts are on the exterior surface of the tire carcass they are exposed to abrasive dirt and foreign material which may shorten the service life of the expensive belt assembly.
Also the two piece belt and tire embodiments depend on contact pressure between the tire carcass and the belt assembly for the transmission of torque as high torque forces present between the vehicle tire and the ground may cause the belt to slip on the tire thus decreasing efficiency. The driving lugs and/or alignment cavities of many contemporary embodiments which are molded into the tread surface of the tire to accommodate complementary protrusions on the exterior belt surface are not necessary with the anchor plate tire as presented herein.
The armored tire of this invention is adapted to be mounted on a wheel for use on an earthworking or transporting vehicle. The tire comprises a carcass portion including a crown section wherein are molded a plurality of anchor plates retained in their location by anchor plies positioned circumferentially around the tire also molded into the crown portion of the tire carcass. Traction shoes or plates are fastened to the molded-in anchor plates and present a traction improving, puncture and damage preventing armored surface.
The attachment of the traction plates to the anchor plates is accomplished through the use of attaching bolts which pass through apertures in the traction plates and then through apertured end spacers carried on the top surface of the anchor plates. Attachment bolts also pass through a center spacer located midway between the end spacers. The bolts passing through the end spacers are retained by means of lock washers and nuts while the bolts passing through the center spacer pass into a threaded lug, hereinafter referred to as a sub-lug, centrally located on the bottom of the anchor plate.
The sub-lug disposition maximizes the central bolt connection as well as providing for the uniform transmission of driving torque. The uniformity of the torque transmission (transmission of torque through the anchor plate at the ends and center portions thereof) will result in a uniform loading of the anchor plate thus increasing the life of the plate. The center spacer and sub-lug, by allowing for a longer bolted connection, will allow for equalization of torque transmission at the center and end points of the anchor plate. The stiffness of all three attaching points are equalized by having the effective volume of each point equalized thus allowing for the equalized spring rates.
The present invention does not depend on external links or independent belts in order to provide attachment of the traction plates to the tire. The belt structure is not necessary as the anchor plates for locating the traction plates are molded into the tire carcass itself. In this embodiment the anchor plates and related anchor plies are not exposed to working environment contaminents and projectiles which may cause damage or premature belt failure.
It is, therefore, an object of this invention to present an armored tire which has track retaining anchor plates molded integrally with the carcass of the tire.
Another significant object of this invention is to present an armored tire that has no external belts, chains, or links.
A further object of this invention is to provide an armored tire that is compatible with large earthmoving vehicles and allows relatively high speed, good shock and vibration dampening characteristics, good tractive efficiency and excellent wear and damage resistance.
Other advantages of the anchor plate tire herein disclosed are that the traction plates which would be fastened to the anchor plates will not move in either a circumferential or lateral direction as may happen with a two piece tire belt design. Also the rotational stability of the anchor plate around its own axis is greatly improved due to the integrity of the design. This consequently improves the stability of any traction plate or grouser plate fastened to the anchor plate.
The life expectency of the anchor plies is also increased as the anchor plies will not be exposed to creeping and rotation of the anchor plates. The rigidity of the anchor plies contributes to decreasing the fatigue of the cables, fabric, and elastomer in the ply thus increasing the life of the tire.
It is further an object of this invention to provide traction plate attaching means having high strength and deflection resistance by the implementation of a centrally disposed sub-lug located on the bottom of the anchor plate. This allows the use of a longer bolt and also allows interchangeability between the outboard bolts and the inboard bolts.
Still another advantage of this invention is the ease of assembly when contrasted to the two piece belt-tire embodiment. The critical relationship between the outside diameter of the tire and the inside diameter of the enveloping belt is not present in the integral anchor plate tire.